The invention relates to lens barrels, and in particular, to lens barrels which is collapsible in digital cameras.
As demand for smaller digital cameras increase, thinner cameras are also emphasized for portability. Thus, thinner lens barrels are required. In a conventional thinner lens barrel, a gap between a lens group and an image-generating device is reduced when not in use, allowing a shorter lens barrel.
In Japan Pub. No. 2003-315861, during receiving, part of photographic lens groups is transferred from an optical axis to provide a thinner lens barrel. In Japan Pub. No. 2004-85934, a thinner cam barrel for extending lens is provided without reducing movement of lens groups.
A conventional focus driving mechanism for driving a focus lens of a digital camera comprises a focus motor parallel to the optical axis, and a screw shaft mechanism mounted at the focus motor. Since the focus driving mechanism occupies the entire length of the focus motor plus that of the screw shaft mechanism along the optical axis, it is difficult to mount the focus driving mechanism inside the thinner lens barrel as disclosed in Japan Pub. No. 2003-315861. In Japan Pub. No 2004-85934, alternatively, the focus driving mechanism is disposed outside the lens barrel; however, this requires an increase in lens barrel size.